Iraqi forces pressed a counter-attack on Saddam Hussein's hometown of Tikrit Sunday as Russia delivered Sukhoi warplanes to aid Baghdad in what diplomats warn is an existential battle against Sunni militants. Swaraj chairs meeting of Gulf envoys to discuss Iraq

Iraqi forces pressed a counter-attack on Saddam Hussein's hometown of Tikrit Sunday as Russia delivered Sukhoi warplanes to aid Baghdad in what diplomats warn is an existential battle against Sunni militants.

Government planes pounded Tikrit with air strikes and clashes broke out across the city Sunday, witnesses said, as thousands of troops advanced in the most ambitious operation Iraqi forces have carried out since insurgents led by the jihadist Islamic State of Iraq and the Levant overran swathes of five provinces weeks earlier.

World leaders, alarmed by the pace of the reverses in Iraq, have meanwhile urged a speeding up of government formation following April elections, warning that the conflict, driven by sectarian divides, cannot be resolved militarily.

Iraqi Shiite fighters secure an area West of the central holy city of Najaf on a road leading to the restive Anbar province. (AFP Photo)

And while beleaguered Prime Minister Nuri al-Maliki has conceded that a political solution is necessary to end the crisis, his security spokesman has for days touted successes in the Tikrit operation that could be crucial not only tactically, but also for morale in the security forces.

"The security forces are advancing from different areas" around Tikrit, lieutenant general Qassem Atta told reporters. "There are ongoing clashes."

Atta said that troops had detonated bombs planted along routes leading to the city, which fell to militants more than two weeks ago.

Witnesses in the city itself, meanwhile, reported waves of government air strikes in various areas of central Tikrit and Saddam's palace compound in the city.

The Iraqi forces, according to Atta, are coordinating with recently-arrived US military advisers in "studying important targets."

Kirkuk advanceAlso Sunday, fighters backed by the Kurdish peshmerga force were advancing on the Shiite-majority village of Basheer, south of Kirkuk that was taken over by militants during the offensive, officials said.

The Tikrit offensive comes as Iraq took delivery of the first batch of Sukhoi warplanes from Russia, with the newly-purchased Su-25 aircraft expected to be pressed into service as soon as possible, bolstering Iraq's air power.

An Iraqi official said that pilots from Saddam's air force would fly the planes.

Su-25s are designed for ground attack, meaning they will be useful for Iraqi forces trying to root out ISIL-led militants from a string of towns and cities they have seized.

Read:Iraq receives Russian jets as it takes fight to militants

In this Saturday, June 28, 2014 photo, Iraqi security forces hold up a flag of the Islamic State in Iraq and the Levant they captured during an operation to regain control of Dallah Abbas north of Baqouba. (AP/PTI photo)

$500 million Sukhoi dealMaliki on Thursday announced that Baghdad was buying more than a dozen Sukhoi aircraft from Russia in a deal that could be worth up to $500 million (368 million euros).

While Washington has been sending military advisers to help Iraqi commanders and is flying armed drones over Baghdad, Iraqi officials have voiced frustration that multi-billion dollar deals for US-made F-16s and Apache helicopters have not been expedited.

Washington, which has pushed for political reconciliation in the face of what Secretary of State John Kerry has described as an "existential" threat, has also so far not acceded to Iraq's appeal for US air strikes.

The US has stopped short of calling for the premier to go but has left little doubt it feels he has squandered the opportunity to rebuild Iraq since American troops withdrew in late-2011.

American officials have also said a proposed $500-million plan to arm and train moderate rebels in neighbouring Syria could also help Iraq fight ISIL, which operates in both countries.

Hundreds of soldiers killedMaliki's security spokesman has said hundreds of soldiers have been killed since the insurgent offensive was launched on June 9, while the UN puts the overall death toll at over 1,000, mostly civilians.

International organisations have urged the establishment of humanitarian corridors to provide aid amid the fighting, with 1.2 million people having been displaced by unrest this year in Iraq.

World leaders have insisted on a political settlement among Iraq's various communities and Grand Ayatollah Ali al-Sistani, revered among the country's Shiite majority, has urged political leaders to quickly form a government after parliament convenes on Tuesday.

Maliki has acknowledged that political measures are necessary, but politicians have nevertheless cautioned that naming a new cabinet could still take a month or more.

Despite unity calls, Iraqi Kurdish leader Massud Barzani has said Baghdad could no longer object to Kurdish self-rule in Kirkuk and other areas from which federal forces withdrew as the insurgents advanced.

Kurdish forces moved into areas vacated by Iraqi federal soldiers, putting them in control of disputed areas that they have long wanted to incorporate into their three-province autonomous region, a move Baghdad strongly opposes.